A communication network includes network elements that route packets through the network, predominantly in line card hardware. To route packets, network elements often utilize intermediate system to intermediate system (ISIS) protocol. Traditionally, ISIS routers are designated as being Level 1 (intra-area); Level 2 (inter-area); or Level 1-2 (both). Level 2 routers are inter-area routers that can only form relationships with other Level 2 routers. Routing information is exchanged between Level 1 routers and other Level 1 routers, and Level 2 routers only exchange information with other Level 2 routers. Level 1-2 routers exchange information with both levels and are used to connect the inter area routers with the intra area routers. In ISIS, area borders are in between routers, designated as Level 2 or Level 1-2. The result is that an ISIS router is only ever a part of a single area. Thus, ISIS traditionally creates a logical topology of a backbone of Level 2 routers with branches of Level 1-2 and Level 1 routers forming the individual areas.
The hierarchy of Level 1 and Level 2 ISIS routers is often present because the number of network elements in a Level 1 ISIS area is limited due to the time it takes for convergence of routing algorithms for an area (e.g., via a shortest path first algorithm). However, such hierarchy requires management of both the Level 1 and Level 2 routing areas which in effect causes artificial partitioning of a network. Over time, these artificial partitions may lead to undesirable management complexity.